Custom Variable Injection

# Custom Variable Injection
Enable the capability for end-users to add additional information to a hook, provided that the hook allows it.

# Example
```properties
/webhook-send customHook customVariable
```

In the example above, the /webhook-send command is used to trigger a custom hook named "customHook" with a custom variable named "customVariable". This syntax allows end-users to inject specific information into the hook, which can then be utilized within the hook's execution logic.